In the past, much effort has been expended in preparing thermally stable polycarbonate compositions which would be color stable at elevated temperatures and particularly at the high molding temperatures generally employed to prepare molded polycarbonate articles. Many different additives have been found that are quite suitable for rendering polycarbonates heat and color stable. Particularly useful are triorgano phosphites such as are disclosed in U.S. Pat. No. 3,305,520. In addition, U.S. Pat. Nos. 3,729,440 and 3,953,388 disclose thermally stable aromatic polycarbonates containing a phosphinite and an epoxy compound. Further, U.S. Pat. No. 3,794,629 discloses chemically stable aromatic polycarbonates containing oxetane phosphites and U.S. Pat. No. 3,978,020 discloses thermally stable aromatic polycarbonates containing phosphonites which include epoxy compounds.
U.S. Pat. No. 3,509,091 discloses stabilized polycarbonate compositions wherein the stabilizer is a cyclic monophosphite compound. While useful, these cyclic monophosphites have low boiling points so that much of the stabilizer is lost during extrusion of the polycarbonate at the relatively high extrusion temperatures typically employed. Thus, such cyclic monophosphite stabilizers are difficult to process and uneconomical to use as they are generally employed in excess amounts in order to incorporate effective stabilizing amounts in the polycarbonate.
Polycarbonates are also used for producing bottles; however, these bottles become hazy after sterilization in water or exposure to moisture at elevated temperatures. U.S. Pat. No. 3,839,247 discloses a water clear polycarbonate composition which can be used to mold bottles wherein the polycarbonate composition contains an aromatic epoxy or an aliphatic epoxy compound as a stabilizer.
Copending application Ser. No. 957,426, filed Nov. 2, 1978, discloses aromatic polycarbonate compositions containing phosphonite oxetanes; copending application Ser. No. 957,429, filed Nov. 2, 1978, discloses aromatic polycarbonate compositions containing a phosphite oxetane containing a hindered phenol; copending application Ser. No. 957,430, filed Nov. 2, 1978, discloses aromatic polycarbonate compositions containing a phenol phosphite or a hindered phenol phosphite; copending application Ser. No. 957,427, filed Nov. 2, 1978, discloses aromatic polycarbonate compositions containing dioxane phosphites, and, copending application Ser. No. 957,428 filed Nov. 2, 1978 discloses aromatic polycarbonate compositions containing a phosphonite or a phosphonite oxetane each of which contains a hindered phenol; each of these copending applications being assigned to the same assignee as this case.